The present invention relates to a method of forming a metal oxide layer, and more particularly, to a method of forming a metal oxide layer, which can be used in a semiconductor device.
A tantalum pentoxide (Ta2O5) film has high dielectric constant and therefore, extensive practical use as a dielectric film in a capacitor for a new generation high-density DRAM of 1 giga bit or more. In order to put a tantalum pentoxide film into practical use, its leakage current characteristics should also be good.
Generally, a tantalum pentoxide film is formed by thermal chemical vapor deposition (CVD). During the thermal CVD, a metal organic precursor, such as Ta(OC2H5)5 as a metal source, and O2 gas are used. However, impurities such as carbon and moisture may be included in the tantalum pentoxide film, which may provide a path for leakage current. Further, once the tantalum pentoxide film is formed, it is amorphous; as a result its film quality may be poor, and it may be difficult to combine with oxygen. Accordingly, electric current flowing through such a film is prone to leak, and oxygen deficiency may occur.
In a conventional method, a low-temperature oxidation annealing process is performed after a tantalum pentoxide film is formed in order to reduce a leakage current in the tantalum pentoxide film and improve the characteristics thereof as a dielectric film. Thereafter, the tantalum pentoxide film is heated at high temperature under an oxygen atmosphere to crystallize the tantalum pentoxide film and remove impurities in the tantalum pentoxide film.
According to the conventional method, a deposition process of forming a tantalum pentoxide (Ta2O5) film and a low-temperature oxidation annealing process for supplementing oxygen deficiency are individually accomplished at different process temperatures. For this reason, two chambers are needed to perform these two processes. If these two processes are to be accomplished in the same chamber, it would take a long time to stabilize the temperature of the chamber. Therefore, time is wasted and throughput decreased.
These problems of the conventional method can occur during the formation of a metal oxide film to be used as a dielectric film in a semiconductor device, as well as in a process of forming a tantalum pentoxide (Ta2O5) film.
At least one embodiment of the present invention provides a method of forming a tantalum pentoxide film, which reduces the time required for an annealing process performed to cure an oxygen deficiency occurring after the formation of the tantalum pentoxide film, thereby enhancing the film characteristics and throughput.
At least one embodiment of the present invention provides a method of forming a dielectric film, for a semiconductor device, using a metal oxide, which enhances the film characteristics and throughput.
At least one embodiment of the present invention provides a method of forming an amorphous tantalum pentoxide or dielectric film where annealing is performed in situ with the formation of the amorphous tantalum pentoxide or metal oxide film.
At least one embodiment of the present invention provides a method of forming an amorphous tantalum pentoxide or dielectric film where annealing is performed at the same or substantially the same temperature as the temperature used during the formation of the amorphous tantalum pentoxide or metal oxide film.
In at least one embodiment of the present invention the activated vapor may be one of O3 gas, UV-O3, O2 plasma, O3 plasma, and N2O plasma. In at least one embodiment of the present invention, the Ta source may be one of Ta(OC2H5)5 and Ta(OC2H5)4OCHCH2N(CH3)2.
In at least one embodiment of the present invention, the concentration of the activated vapor during annealing is the same as or larger than the concentration of the activated vapor used during the deposition of the amorphous tantalum pentoxide film. In at least one embodiment of the present invention, O2 gas as well as the activated vapor may be supplied to the substrate during the annealing. In at least one embodiment of the present invention, the annealing is performed at a temperature of 380-520xc2x0 C. In at least one embodiment of the present invention, the formation of the amorphous tantalum pentoxide film and the annealing may be performed at the same or substantially the same temperature.
In at least one embodiment of the present invention, the annealing may be performed at a higher pressure than the pressure when the amorphous tantalum pentoxide film was formed. For example, the amorphous tantalum pentoxide film may be formed at a pressure of 0.1-10 Torr, and the annealing may be performed at a pressure of 0.1-50 Torr.
In at least one embodiment of the present invention, forming the amorphous tantalum pentoxide film and performing the annealing can be repeated several times until a tantalum pentoxide film is formed to a desired thickness. In at least one embodiment of the present invention, the amorphous tantalum pentoxide film can be crystallized after annealing.
At least one other embodiment of the present invention is directed to a method of forming a tantalum pentoxide film comprising: forming an amorphous pentoxide film on a substrate in a chamber in which an activated vapor atmosphere containing oxygen is maintained, using a Ta source and O2 gas; and annealing the amorphous tantalum pentoxide film in-situ with the formation of the amorphous pentoxide film in an oxygen atmosphere at a lower temperature than the crystallization of tantalum pentoxide.
In yet another embodiment, the chamber can be purged while it is evacuated, between forming the amorphous tantalum pentoxide film and the annealing.
At least one other embodiment of the present invention is directed to a method of forming a dielectric film comprising: forming a metal oxide film on a substrate while the substrate is exposed to a first activated vapor containing oxygen, using a metal organic precursor; and annealing the metal oxide film in-situ with the formation of the metal oxide film while the substrate is exposed to a second activated vapor containing oxygen.
In at least one embodiment of the present invention, the metal oxide film may be one of a tantalum pentoxide film, an aluminum oxide film, a (Ba,Sr)TiO3 (BST) film, and a PbZrTiO3 (PZT) film.
In at least one embodiment of the present invention, during the formation of the metal oxide film, the metal organic precursor, the activated vapor, and O2 gas may be supplied to the substrate. Further, in at least one embodiment of the present invention, during the annealing, the activated vapor and O2 gas may be supplied to the substrate.
In at least one embodiment of the present invention, the formation of the metal oxide film and the annealing may be performed at the same or substantially the same temperature. Also, in at least one embodiment of the present invention, the formation of the metal oxide film and the annealing may be performed in the same chamber while maintaining the vacuum state of the chamber.
At least one other embodiment of the present invention is directed to a method of forming a dielectric film comprising: forming a metal oxide film on a substrate by supplying at least an metal organic precursor and an activated vapor; and annealing the metal oxide film at substantially the same temperature as the a temperature used to form the metal oxide film.
At least one other embodiment of the present invention is directed to a method of forming a dielectric film comprising: forming a metal oxide film on a substrate by supplying at least an metal organic precursor and an activated vapor, under a first pressure, a first vapor concentration, and a first vapor flow rate; and annealing the metal oxide film under a second pressure, a second vapor concentration, and a second vapor flow rate, wherein at least one of the second pressure, second vapor concentration, and second vapor flow rate is different from the first pressure, the first vapor concentration, and the first vapor flow rate used to form the metal oxide film.
According to one or more embodiments of the present invention, in order to form a dielectric film composed of a metal oxide, little or no additional time is required to stabilize the temperature of the chamber during the deposition of an amorphous dielectric film and a subsequent annealing, thereby raising throughput. Also, during the deposition of the amorphous dielectric film and the subsequent annealing, it is possible to improve deposition characteristics such as step coverage and deposition rate and electric characteristics such as leakage current characteristics by appropriately controlling the concentration of activated vapor containing oxygen and the flow rate and pressure of O2 gas.